DE-A1-25 20 255 describes a light building element composed of construction elements, in which roofing plates and stiffening constitute an integrated unit, such as a pre-manufactured roof plate element, each consisting of at least one open basic profile glued directly on an upper cover plate constituting both covering and load compressive element, and where the cover plate is broader than the basic profile and extends outside the basic profile along both longitudinal edges.
EP-A1-0 675 990 (WO 92/19826) discloses a premanufactured roof plate element comprising three boxshaped, carrying basic profiles of steel plate, which upwardly is directly connected with a compressive force plate consisting of strong construction plywood, and having the same width as the basic profiles, which are placed along opposite long sides and in the middle of the roof plate element.
Common for these known light roof plate elements is, that they have a relative large overall height, which during manufacturing, storage and transport cause extraordinary large demands for space. Also by projecting and the construction work it is inexpedient, that the overall height of the roof plate element itself is large, as it causes extra costs for obtaining extra free height.
The invention has for its purpose to provide an improved premanufactured roof plate element of the type mentioned in the introductory part, and which by means of simple provisions makes it possible to reduce the overall height of the roof plate element itself.
The roof plate element according to the invention is distinctive in that said compressive force plate consists of a steel plate, which--seen in cross section--is corrugated. By means of simple provisions it is hereby obtained, that it becomes possible to reduce the overall height and the weight of the roof plate element, which may result in considerable savings by transport and storage of finished pre-manufactured roof plate elements. However, it is of most importance that a roof plate element according to the invention may be produced totally without use of organic material. In order to further reduce the overall height of the roof plate element itself, it may be advantageously, that also a bottom side part of said boxshaped girders--seen in a cross section--also is corrugated.
In order to give the boxshaped girder by the roof plate element according to the invention better side stability it may be appropriately, that said compressive force steel plate has longitudinal, folded side edges extending downwards along opposite vertical sides of the girder.
The roof plate element according to the invention may be such provided that the corrugation of said compressive force plate is trapezoid, or the corrugation may be wave-shaped. Besides the same concerns said bottom side part of the girder. By corrugation of top and bottom side parts of the girder a better stability is obtained for both upwards and downwards directed forces in connection with loads and gust of wind.
Furthermore the invention relates to a boxshaped girder of the type mentioned in the introductory part of claim 5 by way of example for use in a roof plate element according to the invention, which girder is distinctive in, that the compressive force plate consists of a steel plate, which--seen in cross section--is corrugated.
The overall height of the girder according to the invention may be further reduced, if the girder is such provided, that a bottom side part of said boxshaped girders--seen in cross section--also is corrugated.
In order to further improve the load capacity and the side stability of the girder according to the invention, it may be advantageously be such provided, that said compressive force steel plate has longitudinal, folded side edges extending downwards along opposite vertical sides of the girder.
The girder according to the invention is preferably such provided that the corrugation of said compressive force plate is trapezoid, or said corrugation of said compressive force plate may be wave-shaped.
The invention is explained in more detail in the following with reference to the drawing, in which: